A continuing longitudinal study is planned to measure blood pressure, height, weight and skinfold thickness of 1223 children (476 black, 747 white), twice annually, for 5 years and to continue to measure Type A behavior in 618 children annually. The study sample is a stable population of children selected from more than 98% of 10,500 children being all children in grades 1, 2, and 3 of the Minneapolis Public School System in the Spring of 1978. All children from the top and bottom 5% of the systolic blood pressure (BP) distribution and a 1/2 sample of black children and a 1/9 sample of white children from the rest of the BP distribution were followed 2x per year in spring and fall of 1978, 1979, and 1980 for BP and body size measurements. These 1200+ children have also been visited at home and extensive psychological, medical history, dietary history, demographic data, and overnight urine collections for Na+, K+ and creatinine have been gathered. In addition blood pressure, height, weight, medical history, psychological data and Life Event data have been gathered on the parents. In 1981 no screening was performed but consent was obtained to continue screening throughout the remaining years of school. In 1982, 22+ Na red blood cell (rbc) efflux rate was measured in 395 children and 602 parents. In addition, Type A behavior patterns were measured in 618 children and their parents. During the course of the study baseline data and laboratory and Type A classification data will be used to develop predictive equations for blood pressure levels in the highest percentiles in late adolescence. This will include derivation of an index of "tracking" and the predictive value of this index. These may provide etiological clues to essential hypertension and allow in depth study of other factors among children to be found at highest risk. From such proposed predictive studies it will be possible to develop strategies for primary prevention and more intricate examination of etiological factors. During the first phase of this study 1978-80 subsamples of children were examined to determine psychological antecedents of Type A behavior in adults and differences in the sympathetic nervous system and renin-angiotension system between children with relatively high and low blood pressure. The Type A studies will be expanded in the present study.